Here’s a great article on how to use the new SQL Server 2008 geography data type for proximity searches aka zip code radius search.   I’ve used many of diffent ways to run these searches, including the ones provided by the zip code data providers, but this solution has got to be the fastest I’ve run across.   If you use SQL Server 2008 and need a quick and simple proximity search based on zip code, then you have to read this article:  http://blogs.lessthandot.com/index.php/DataMgmt/DataDesign/sql-server-2008-proximity-search-with-th

If you have SQL 2005, then read this  article:  http://blogs.lessthandot.com/index.php/DataMgmt/DataDesign/sql-server-zipcode-latitude-longitude-pr

I love finding solutions that make life easier.